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bpd · Sep 8, 2009, 09:07 PM

I recently had to perform minor surgery on my Mac Pro (2007 version) in order to replace the battery on the Apple Pro RAID card, which had gone bad. In order to do this, I had to remove the front fan casing.

Upon putting everything back together, I almost immediately noticed that the fan noise was now far louder than it ever had been in the past.

I did some research, which led to me installing smcFanControl. According to smc, the fan is running at the minimum 500 RPM. However, when I increased the fan speed setting to 2800 RPM and listened carefully to the fan as the speed ramped up, I hear no change in pitch until the smc display indicates about 1500 RPM. My only current thought is that the machine believes it's driving the fan at 500 RPM, when in actuality it's going far faster.

I opened the Mac back up and pulled out the fan casing again, and looked carefully to see if anything looked amiss, and I found a wire on a 4-wire connector that looked like it had been cut. It's one of two connectors directly above the 2 internal unused SATA ports, but they're not connectors I'm familiar with. The label next to the connectors says "SNS". But I haven't been able to find any info anywhere that would give me a clue what these ports are for, or if the broken wire may be a source of my problem, or of some other problem I don't even know about.

Please see the image at: http://i844.photobucket.com/albums/a...roken-wire.jpg

Anyone have any idea what this connector is, and if it might be related to my fan problem?

thanks,
Ben

cgc · Sep 8, 2009, 09:17 PM

Originally Posted by bpd

I recently had to perform minor surgery on my Mac Pro (2007 version) in order to replace the battery on the Apple Pro RAID card, which had gone bad. In order to do this, I had to remove the front fan casing.

Upon putting everything back together, I almost immediately noticed that the fan noise was now far louder than it ever had been in the past.

I did some research, which led to me installing smcFanControl. According to smc, the fan is running at the minimum 500 RPM. However, when I increased the fan speed setting to 2800 RPM and listened carefully to the fan as the speed ramped up, I hear no change in pitch until the smc display indicates about 1500 RPM. My only current thought is that the machine believes it's driving the fan at 500 RPM, when in actuality it's going far faster.

I opened the Mac back up and pulled out the fan casing again, and looked carefully to see if anything looked amiss, and I found a wire on a 4-wire connector that looked like it had been cut. It's one of two connectors directly above the 2 internal unused SATA ports, but they're not connectors I'm familiar with. The label next to the connectors says "SNS". But I haven't been able to find any info anywhere that would give me a clue what these ports are for, or if the broken wire may be a source of my problem, or of some other problem I don't even know about.

Please see the image at: http://i844.photobucket.com/albums/a...roken-wire.jpg

Anyone have any idea what this connector is, and if it might be related to my fan problem?

thanks,
Ben

It looks like the dangling wire should logically connect to the broken wire on the connector...why you scared to connect them?

bpd · Sep 8, 2009, 09:44 PM

I'm not scared to connect them -- I just have no good way to do so. The wire has been cut, and it is not trivial to repair. There's not enough of the wire left on the connector side to strip and wind together with the dangling end.

reader50 · Sep 9, 2009, 12:47 AM

Solder it back. If you aren't handy with a soldering iron, ask around. One of your friends may be.

If it really can't be stretched back to solder, then use a little new wire to bridge the gap. Use liquid electrical tape to restore the missing insulation afterwards.

bpd · Sep 9, 2009, 07:44 AM

Still, no one has answered my original question. What IS this connector?

imitchellg5 · Sep 9, 2009, 09:14 AM

Just part of the cable that controls the fan I assume.

bpd · Sep 9, 2009, 09:50 AM

Okay, I got my hands on a Mac Pro service manual, and the mystery is solved. The two identical connectors are labeled HDD_SNS and ODD_SNS. And they are the HDD thermal sensor and ambient intake thermal sensor, respectively. Time to go solders some wires.

cgc · Sep 9, 2009, 10:05 AM

Oh...so they do control the fan... It's good to be cautious with an expensive piece of electronics, but this was nearly a sure thing considering what happened.

Soldering isn't too hard (especially things that aren't very heat sensitive) but if you're not too good at it you could either get someone to help or you could get some spare wire and practice as reader50 suggested.

Hope the sarcasm didn't upset you...we come in peace, we come in peace (quote from "Mars Attacks")